Mixed conditional: not so traditional use of past continuous

Hi. I think the verb in the if-clause is in a past continuous tense. But unlike the time frame a past continuous tense commonly inhabits or plays out in every day writing (if I said it correctly to reflect what I wanted to say), this use is not in the realm of the past (if I am not mistaken) but in a present hypothetical realm. What do you think? Also, could we put time phrases like the one in parentheses, "two days ago," in the main clause?

If he weren't playing tennis with John next week, he would have said OK to a dinner meeting (two days ago).